Water-based ink composition with color-changing by evaporation

Abstract

The present disclosure concerns a water-based color-changing ink composition with two different states of color over time, an initial color A and then a second color B which is not colorless, comprising a volatile pH-modifier base capable of evaporating at room temperature (20° C.), a pH-sensitive dye, and an optional non-pH sensitive dye. The disclosure also concerns a method for preparing such color-changing ink composition. A writing instrument comprising such color-changing ink composition, and a kit comprising such color-changing ink composition and an eradicator, as well as methods for writing on a substrate, are also part of the disclosure. Finally, the disclosure aims at a substrate coated with a color-changing ink composition according to the disclosure.

We claim: 
     
         1 - 15 . (canceled) 
     
     
         16 . A color-changing ink composition with two different states of color over time, an initial color A and then a second color B which is not colorless, comprising:
 (a) water,   (b) at least one volatile pH-modifier base capable of evaporating at room temperature (20° C.), and   (c) at least one first pH-sensitive dye.   
     
     
         17 . The color-changing ink composition according to  claim 16 , wherein the ink composition is exempt of eradicator agent. 
     
     
         18 . The color-changing ink composition according to  claim 16 , wherein the at least one volatile pH-modifier base (b) has a vapor pressure ranging from 1 kPa to 1,000 kPa at room temperature (20° C.) and at constant air pressure. 
     
     
         19 . The color-changing ink composition according to  claim 16 , wherein the at least one volatile pH-modifier base (b) has a boiling point of higher than -10° C. and of below 10° C. 
     
     
         20 . The color-changing ink composition according to  claim 16 , wherein the at least one volatile pH-modifier base (b) is an aliphatic amine. 
     
     
         21 . The color-changing ink composition according to  claim 16 , wherein the at least one volatile pH-modifier base (b) is a secondary aliphatic amine in C 1 -C 6 . 
     
     
         22 . The color-changing ink composition according to  claim 16 , wherein the at least one volatile pH-modifier base (b) is chosen in the group consisting of methylamine, dimethylamine, diethylamine, triethylamine, or mixtures thereof. 
     
     
         23 . The color-changing ink composition according to  claim 16 , wherein the at least one volatile pH-modifier base (b) is chosen in the group consisting of dimethylamine and/or diethylamine. 
     
     
         24 . The color-changing ink composition according to  claim 16 , wherein the ink composition further comprises at least one non-pH sensitive dye (d) and/or at least one second pH-sensitive dye (e) which is always in a colored state. 
     
     
         25 . The color-changing ink composition according to  claim 24 , wherein the least one first pH-sensitive dye (c) is chosen in the group consisting of acid dyes, basic dyes, direct dyes, mordant dyes; food dyes, and mixtures thereof. 
     
     
         26 . The color-changing ink composition according to  claim 16 , wherein the least one first pH-sensitive dye (c) is always in a colored state. 
     
     
         27 . The color-changing ink composition according to  claim 26 , wherein the least one first pH-sensitive dye (c) is chosen in the group consisting of acid dyes, basic dyes, direct dyes, mordant dyes; food dyes, and mixtures thereof. 
     
     
         28 . The color-changing ink composition according to  claim 26 , wherein the composition is exempt of non-pH sensitive dye (d). 
     
     
         29 . The color-changing ink composition according to  claim 16 , wherein the content of volatile pH-modifier base(s) (b) ranges from 0.8 to 6% by weight, relative to the total weight of the ink composition. 
     
     
         30 . The color-changing ink composition according to  claim 16 , wherein the content of volatile pH-modifier base(s) (b) ranges from 1.6 to 4.8% by weight, relative to the total weight of the ink composition. 
     
     
         31 . The color-changing ink composition according to  claim 16 , wherein the total content of pH-sensitive dye(s) (first pH-sensitive dye (c) and optional second pH-sensitive dye(s) (e) which is always in a colored state) ranges from 0.1 to 15% by weight, relative to the total weight of the ink composition. 
     
     
         32 . The writing instrument comprising a color-changing ink composition according to  claim 16 , wherein the writing instrument is a pen. 
     
     
         33 . A method for writing with a writing instrument according to  claim 32 , comprising the step of writing on a substrate with a writing instrument according to  claim 32 , the ink composition writing having an initial color A when applied to the substrate which changes, at room temperature (20° C.), to a second color B, which is different from initial (first) color A and which is not colorless. 
     
     
         34 . The method for writing with a writing instrument according to  claim 33 , the ink composition writing having an initial color A when applied to the substrate which changes, at room temperature (20° C.), to a second color B, which is different from initial (first) color A and which is not colorless, the color-change occurring within at least 10 seconds, after application to the substrate and/or within 30 minutes, after application to the substrate. 
     
     
         35 . A kit comprising:
 a writing instrument according to  claim 32 , and
 an eradicator.